DNS Nameserver Lookup & Validation Tool

Perform deep, authoritative DNS nameserver resolution. Trace delegation paths from root servers, inspect glue records, and validate NS configuration against RFC 1034/1035 standards to prevent zone poisoning and resolution failures.

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What Is a DNS Nameserver?

A DNS Nameserver (NS record) is an authoritative server that holds DNS zone records for a domain. NS records delegate authority over a domain to specific servers. Multiple NS records provide redundancy — if one fails, others continue resolving queries.

Why Nameserver Delegation Matters

Incorrect NS delegation — lame servers, mismatched glue records, or single points of failure — causes complete DNS resolution failure. Without proper NS redundancy, your domain becomes unreachable if one server goes offline.

Common NS Configuration Mistakes

Hosting all NS records on the same subnet (single point of failure), missing in-bailiwick glue records, parent-child NS mismatches, and lame delegations returning SERVFAIL are the most critical NS misconfigurations.

ROOT_HINT

TLD_REFERRAL

NS_QUERY

GLUE_RESOLVED

NS_LOOKUP_V1

AUTHORITY_FOUND

How It Works

Query Root Servers

Initiates a recursive trace from the DNS root to retrieve the TLD referral and identify all delegated nameservers.

Fetch TLD Delegation

Queries the TLD nameservers to retrieve the delegated NS records and glue address records for your domain.

Query Authoritative Servers

Directly queries each delegated nameserver to verify it responds authoritatively and returns consistent zone data.

Compare & Validate

Cross-references parent zone delegation with child zone NS records to detect mismatches, lame delegations, and missing glue.

Deep Delegation Trace

Traces the complete DNS resolution path from root servers through TLD to your authoritative nameservers, visualizing each referral step.

Glue Record Inspection

Extracts and validates in-bailiwick glue records provided by the parent zone, ensuring nameservers with names inside the zone have correct A/AAAA addresses.

Parent-Child Consistency

Identifies discrepancies between NS records delegated by the parent TLD and the NS records served by your own authoritative nameservers.

RFC 2182 Redundancy Analysis

Evaluates nameserver diversity by checking if NS hosts are distributed across different IP subnets and autonomous systems for true fault tolerance.

Lame Delegation Detection

Automatically flags nameservers that refuse queries or return non-authoritative responses, indicating misconfigured or abandoned delegations.

IPv6 Resolution Readiness

Checks for the presence and validity of AAAA glue records to ensure your domain resolves correctly over pure IPv6 networks.

Frequently Asked Questions

What is a DNS nameserver lookup?

A DNS nameserver lookup queries the Domain Name System to identify the authoritative servers responsible for a specific domain. It traces the delegation path from the root, through the TLD, down to the specific nameservers configured for the domain, ensuring that queries are routed correctly to retrieve zone data.

What is a lame delegation in DNS?

A lame delegation occurs when a parent zone (like a TLD) delegates authority for a domain to a nameserver, but that nameserver is not configured to answer authoritatively for the domain. This can result in SERVFAIL errors, slow resolution times, and potential vulnerabilities to DNS hijacking.

Why do parent and child NS records need to match?

Consistency between parent (TLD) and child (zone apex) NS records is critical for predictable DNS resolution. If they mismatch, resolvers may cache the incorrect set depending on how they query the domain, leading to intermittent resolution failures or delayed propagation during DNS migrations.

What are glue records and why are they important?

Glue records are A or AAAA records provided by the parent zone when the authoritative nameserver for a domain is a subdomain of that same domain (in-bailiwick). They prevent circular dependencies, ensuring that a resolver can find the IP address of the nameserver in order to query it for the domain's records.

How many nameservers should a domain have?

RFC 2182 recommends a minimum of two authoritative nameservers, preferably geographically dispersed and hosted on different ASNs. This redundancy ensures that if one nameserver or network segment fails, the domain remains resolvable and accessible.

What is the difference between recursive and authoritative nameservers?

Recursive nameservers (resolvers) traverse the DNS hierarchy on behalf of a client to find the IP address of a domain. Authoritative nameservers hold the actual DNS records (like A, MX, TXT) for a domain and provide definitive answers to recursive resolvers without querying other servers.

Can I use IP addresses instead of hostnames for NS records?

No, per RFC 1035, the RDATA of an NS record must contain a valid domain name (hostname), not an IP address. The mapping of that hostname to an IP address is handled by A and AAAA records, which may be supplied as glue records by the parent zone.